1. Field of the Invention
This invention relates to antibiotic carriers which exhibit optimal water absorption/retention properties for the promotion of wound healing and a method of treating wounds utilizing such carriers.
2. Description of the Related Art
While minor cuts, burns and abrasions seldom become infected, any break in the skin can lead to localized or even systemic infection. This is of special concern in children who may not have fully developed immune systems, or in immunocompromised individuals.
Recently, it has been shown that the amount of moisture retained in equilibrium with wounded skin, i.e., cuts, burns and abrasions, dramatically alters the healing of the wound. While an uncovered wound or loosely covered wound--exemplified by a minor cut or abrasion covered only by a flexible fabric bandage--will quickly form a hard crust or scab, this represents the least favorable environment for quick healing with minimal scarring. The only advantage of hard crust formation is that the wound tissue is thoroughly sealed from contamination by pathogens from the environment or adjacent intact skin. The disadvantage of the body's naturally evolved healing process is that fibroblasts, macrophages and other cellular repair mediators can only slowly migrate to, and function in, the wound area that is covered by dry crust. Limited mobility of fibroblast results in abnormal collagen production in the dermis which results in scarring. It is important to understand that the human body's only mechanism of infection prophylaxis, namely scabbing, results in extended time to healing of the wound and increased dermal scarring upon completion of the healing process.
The ideal environment for wound healing is a moist environment. Ideally, the moist environment should provide sufficient fluid such that the mobility of tissue repair mediators is not limited, but not so much fluid that these mediators are expelled from the tissue being repaired. It is also important that the surrounding skin not contract toward the wound as this increases the amount of scarring. As described above for an uncovered or loosely covered cut or minor abrasion, the scab results in a dry wound environment that does not have sufficient fluid to allow optimal mobilization of tissue repair mediators. Conversely, more extensive abrasions and burns, particularly after an initial hypoprofusion state, can be highly exuding wounds that are "too wet," resulting in expulsion of tissue repair mediators. Optimal therapy of these wounds requires that a significant amount of the water be removed from the wound while the tissue repair mediators remain mobile and in contact with the wounded tissue.
Thus, for optimal healing, i.e., rapid healing with minimal scarring, a controlled moist environment must be maintained such that moisture is allowed to permeate a wound which becomes too dry (i.e., dry crust or scab forming) and also allowed to escape from a wound which becomes too wet (i.e., heavily exudating), and that surrounding skin is not prompted to contract toward the wound.
While this moisture balance for a wound can be accomplished using semipermeable wound dressings, such coverings may actually hinder the healing process when placed in direct contact with the wound site. In particular, the wounded skin or repair mediators may attach to the bandage matrix resulting in introduction of a new wound upon dressing removal, or at least immobilization or removal of repair mediators. Also, semi-permeable wound dressings provide no prophylaxis against infection. As a consequence, the wound is highly prone to microbial colonization and possible infection during the healing process. Finally, wound dressings tend to be expensive, not only in terms of the cost of materials, but also in terms of the nursing time required for dressing changes.
In consideration of cost, ease of use, prophylaxis of infection, and provision of an optimal wound healing environment, the preferred treatment of wounds would be a topical semisolid containing antimicrobial actives having a broad defense against infection and being capable of maintaining a moist wound environment by promoting increased water content in wounds becoming dry and promoting reduction of water content in wounds becoming too wet. In the past, triple antibiotic topicals prepared in hydrophobic ointment vehicles have been used to provide prophylaxis against infection and promote increased water retention in wounds due to the occlusive nature of the hydrophobic ointment system. However, these products cannot promote reduction of water content in wounds which are highly exudating, because the ointment floats to the top of the exudate and is removed from the wound site. Thus, triple antibiotic topicals formulated in hydrophobic ointments are inappropriate for use on highly exudating wounds (i.e., burns and deep abrasions) because the product is quickly removed from the wound site making it ineffective both for infection prophylaxis and optimal wound healing.
Better carriers are needed for the triple antibiotic agents. Such topical semisolid compositions need to retain as much of their application weight as possible upon drying to prevent surrounding skin from contracting toward the wound.